The overall objective of the Neuropathology Core (B) is to prepare and interpret neuropathologic material derived from the various experiments described in Projects 1-5. Specific aims include: histologic processing of brain specimens for light and electron microscopy, and expert interpretation of neuropathologic alterations arising from cerebral hypoxia-ischemia. Brains to be studied will include those of newborn dogs previously subjected to hypothermia or hypothermic circulatory arrest and of developing postnatal rats previously subjected to cerebral hypoxia-ischemia. Brains will be fixed in situ by either perfusion- fixation or by immersion using a variety of fixatives. Thereafter, brains will be examined grossly and microscopically, and the extent of damage determined by specific scoring methods. Histologic processing will include those techniques required for paraffin or resin embedding followed by tissue sectioning. A variety of stains will be used to accentuate morphologic alterations. Histologic interpretation will be conducted by the Principal Investigator (Dr. Towfighi) in collaboration with the Principal Investigators of the individual Projects. In addition to his collaborative efforts with the individual Projects, Dr. Towfighi also will be responsible for the conduct of specific experiments including: 1) the evolution of hypoxic-ischemic brain damage in the immature rat; and 2) the nature and distribution of histologic alterations arising from cerebral hypoxia-ischemia in developing rats from 10 through 28 days of postnatal age.